Electrochemical storage cell containing at least one electrode formulated from a phenylene-thienyl based polymer

ABSTRACT

An electrochemical storage cell or battery including as at least one electrode at least one electrically conductive polymer, the polymer being poly(1,4-bis(2-thienyl)-3-fluorophenylene), poly(1,4-bis(2-thienyl)-2,5-difluorophenylene), poly(1,4-bis(2-thienyl)-2,3,5,6-tetrafluorophenylene), or poly(1,4-bis(2-thienyl)-benzene). These polymeric electrodes have remarkably high charge capacities, and excellent cycling efficiency. The provision of these polymeric electrodes further permits the electrochemical storage cell to be substantially free of metal components, thereby improving handling of the storage cell and obviating safety and environmental concerns associated with alternative secondary battery technology.

ORIGINATION OF THE INVENTION

The work that resulted in the subject invention was supported by GrantNo. FA8002-96-C-0301, with the U.S. Department of the Air Force as thesponsoring government agency.

This is a Continuation-in-Part of National application Ser. No.08/741,015 filed Oct. 30, 1996, now U.S. Pat. No. 5,733,683.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a battery or electrochemical storagecell, in particular a secondary cell, containing at least one electrodeprepared from at least one electrically conductive and electrochemicallyoxidizable and/or reducible polymer. The battery or electrochemicalstorage cell of the present invention can be at least substantiallyfree, or completely free, of metal components.

2. Description of the Related Art

Since the discovery that polymeric materials, and in particularpolyacetylene, could be reversibly doped and undoped and thus employedas electrode materials for charge storage applications, muchconsideration and investigation has been directed towards employingpolymers in a wide variety of electrical and electronic deviceapplications, including energy storage (R. B. Kaner et al., J. Phys.Chem., 90, 5102 (1989); K. Kaneto et al. Japn. J. Appl. Phys., 22, L567(1983)), light emitting diodes (D. Braun et al., Appl. Phys. Lett., 58,1982 (1991); J. J. M. Halls et al. Nature, 376, 498 (1995); M. Granstromet al., Science, 267, 1479 (1995)), sensors (J. W. Thackeray et al., J.Phys. Chem., 89, 5133 (1985); G. Fortier et al., Biosensors andBioelectronics, 5, 473 (1990); P. N. Bartlett et al., J. Electroanal.Chem., 224, 27 (1987)), and electrochromic devices (H. Yashima et al.,J. Electrochem. Soc., 134, 46 (1987); M. Gazard, Handbook of ConductingPolymers, Vol. 1, ed. (1983)).

The conductivity of neutral polymers can be dramatically increased bychemically doping the polymers in a controlled manner with electronacceptor and/or electron donor dopants. The term doping used inconnection with conducting polymers refers to the partial oxidation(p-doping) or partial reduction (n-doping) of the polymer, combined withthe associated transport of charge compensating dopant ions into or outof the polymer. Conducting polymers are characterized by their abilityto be switched between a neutral (or insulating) state and one or moredoped (conducting) state(s).

In charge storage applications, such as electrochemical secondarystorage cells, electrode materials should be able to undergo multipledoping and undoping cycles with high utilization efficiency and chemicalstability. In addition, the two electrode materials should have a highcharge capacity and combine to exhibit a high cell voltage.

Polyacetylene, polypyrrole, polyaniline, polythienylene, andpolythiophene are among the several polymers that have been investigatedand drawn intense interest to date in connection with charge storageapplications. For example, a polymeric storage cell with a polypyrrole(cathode) electrode and polypyrrole/polystyrene sulfonate (anode)electrode is described in U.S. Pat. No. 5,637,421 to Poehler et al., thecomplete disclosure of which is hereby incorporated by reference.

However, repeated doping and undoping during charging and/or dischargemay cause degradation of the polymer. Many polymers, such aspolyacetylene, have been plagued by poor charge/discharge cyclingcharacteristics (i.e., reversibility) due to inferior chemical andelectrochemical stability. For instance, while improvement in chargecapacity and reversibility has been reported in connection with thep-doping of poly(3(4-fluorophenyl)thiophene), this polythiophenederivative exhibits relatively low charge capacity and poorreversibility when n-doped.

Thus, while some progress has been made in understanding conductionmechanisms, electronic structure, doping characteristics, and opticalproperties in conductive polymers, there remains the need to developimproved polymeric electrodes for electrochemical storage cells thatexhibit suitable charge capacities and reversibilities in both then-doped and p-doped states and can be employed in commercialapplications without the need for metallic components.

SUMMARY OF THE INVENTION

It is therefore an objective of the present invention to solve theaforementioned problems associated with the related art as well as otherproblems by providing an electrochemical storage cell containingelectrode materials that can undergo multiple doping and undoping cycleswith high cycling efficiency and chemical stability.

It is another objective of the present invention to provide anelectrochemical storage cell containing polymeric materials adaptablefor preparing anodes and cathodes having high charge capacities, andthat, when used in combination, yield a high cell voltage.

It is yet another objective of the present invention to providepolymeric electrode materials that can be incorporated into anelectrochemical storage cell without the provision of any, or at leastsubstantially no, metallic components or metal ions and yet achieve anexcellent cell voltage.

Still another objective of the present invention is to provide aconstruction for an electrochemical storage cell that permits the celldesign to be lightweight and flexible and overcomes safety andenvironmental concerns associated with alternative secondary batterytechnology.

Guided by the aforementioned objectives, the present inventorssynthesized: (1) a series of fluorophenyl thiophene polymers by devisingpreparatory techniques to systematically vary the number and position ofthe fluorine on the phenyl group; and (2) a series of differentphenylene-thienyl based polymers by devising preparatory techniques tosystematically vary the number and position of the fluorine on thephenyl group.

As a result of this undertaking, the present inventors discovered thatpolymeric electrodes exhibiting improved charge capacities andreversibilities in both the n-doped and p-doped states could be achievedby preparing at least one of the electrodes from at least oneelectrically conductive fluorophenyl thiophene polymer selected from thegroup consisting of:

poly(3(2-fluorophenyl)thiophene),

poly(3(3-fluorophenyl)thiophene),

poly(3(2,4-difluorophenyl)thiophene),

poly(3(3,4-difluorophenyl)thiophene),

poly(3(3,5-difluorophenyl)thiophene), and

poly(3(3,4,5-trifluorophenyl)thiophene).

Also, as a result of this undertaking, the present inventors discoveredthat polymeric electrodes exhibiting improved charge capacities andreversibilities in the p-doped state could be achieved by preparing atleast one of the electrodes from at least one electrically conductivephenylene-thienyl based polymer selected from the group consisting of:

(i) poly(1,4-bis(2-thienyl)-benzene);

(ii) poly(1,4-bis(2-thienyl)-3-fluorophenylene);

(iii) poly(1,4-bis(2-thienyl)-2,5-difluorophenylene); and

(iv) poly(1,4-bis(2-thienyl)-2,3,5,6-tetrafluorophenylene).

It appears that the phenylene-thienyl based polymers may also exhibitimproved charge capacities and reversibilities in the n-doped state,depending on the electrolyte solvent that is used.

Accordingly, the present invention is directed to polymeric electrodesprepared from at least one of the foregoing fluorophenyl thiophenepolymers, or at least one of the foregoing phenylene-thienyl basedpolymers, or a blend of one or more of both of the foregoingfluorophenyl thiophene polymers and phenylene-thienyl based polymers.

The present invention further relates to an electrochemical storage cellincluding at least one electrode prepared from at least one of theabove-mentioned fluorophenyl thiophene polymers, or at least one of theforegoing phenylene-thienyl based polymers, or a blend of one or more ofboth of the foregoing fluorophenyl thiophene polymers andphenylene-thienyl based polymers.

In a first preferred embodiment of the invention,poly(3(3,4,5-trifluorophenyl)thiophene) is selected as the electricallyconductive polymer of the anode, and poly (3(3,5-difluorophenyl)thiophene) is selected as the electrically conductive polymer ofthe cathode. In a second and most preferred embodiment of the invention,poly (3(3,4,5-trifluoro-phenyl)thiophene) is selected as theelectrically conductive polymer of the anode, and at least one of thephenylene-thienyl based polymers is selected as the electricallyconductive polymer of the cathode.

Optionally, a substantially metal-free cell can be constructed byproviding non-metallic current collectors and supports, such as graphitecurrent collectors and poly(tetrafluoroethylene) (TEFLON) supports.Moreover, the electrolyte can be prepared from a polymer gel film, suchas poly(acrylonitrile) with tetrabutylammonium tetrafluoroborate salt ina propylene carbonate solvent.

Since the cells of the present invention can be fabricated from multiplepolymer films, the cells are lightweight and flexible and do not havethe safety and environmental concerns associated with conventional highperformance batteries. The elimination of any metallic components orliquid phases provides a unique alternative for secondary batterytechnology.

Further, since the components of the cell of the present invention areboth moldable into various shapes and flexible, the cell can beincorporated into a device as a lining, and therefore takes up much lessspace in the device. This feature makes the electrochemical cell of thepresent invention especially adaptable for application inbattery-operated automobiles and satellites, and other compact devices.

The present invention still further relates to batteries containing theelectrolyte storage cells of the present invention. The battery may beeither of a single cell structure or a multi-layer cell structure, andcan be practiced as a primary or secondary battery.

These and other objects, features, and advantages of the presentinvention will become apparent from the following detailed descriptionwhen taken in conjunction with the accompanying drawings whichillustrate, by way of example, the principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate the present invention. In suchdrawings:

FIG. 1 is an exploded view of the construction of an electrochemicalstorage cell in accordance with one or more embodiments of the presentinvention;

FIG. 2A is a schematic view representing the molecular structure of a3(3,4,5-trifluorophenyl)thiophene monomer, and FIG. 2B is a schematicview representing an electrically conducting polymer having a backboneof 3(3,4,5-trifluoro phenyl)thiophene;

FIG. 3A is a schematic view representing the molecular structure of3(3,5-difluorophenyl)thiophene monomer, and FIG. 3B is a schematic viewrepresenting an electrically conducting polymer having a backbone of3(3,5-difluorophenyl)thiophene;

FIG. 4 is a voltammogram illustrating the electrochemical propertiesexhibited from n-doping/undoping poly(3(3,4,5-trifluorophenyl)thiophene)and p-doping/undoping poly(3(3,5-difluorophenyl)thiophene) in 0.25Mtetrabutylammonium tetrafluoroborate in propylene carbonate;

FIG. 5 is an Arrhenius plot of the conductivity of an ionicallyconducting polymer gel electrolyte as a function of temperature;

FIGS. 6A and 6B are graphs representing voltage versus capacitydischarge curve for an electrochemical storage cell in accordance withan embodiment of the present invention depicted in FIG. 1;

FIG. 7A (i-iv) shows the molecular structures of phenylene-thienyl basedmonomers and FIG. 7B (i-iv) shows schematic illustrations ofelectrically conducting polymers having a backbone with thephenylene-thienyl based monomers;

FIG. 8 is a voltammogram illustrating the electrochemical propertiesexhibited from p-doping/undoping 1,4-bis (2-thienyl)-3-fluorophenyleneand n-doping/undoping poly (3(3,4,5-trifluorophenyl) thiophene) in 0.25Mtetrabutyl ammonium tetrafluoroborate in propylene carbonate;

FIG. 9 is a graph representing voltage versus capacity discharge curvefor an electrochemical storage cell in accordance with an embodiment ofthe present invention depicted in FIG. 1; and

FIGS. 10A and 10B are graphs representing voltage versus time dischargecurve for an electrochemical storage cell in accordance with anembodiment of the present invention depicted in FIG. 1, including theinset representing the relationship between charge time and voltage(dotted line) and discharge time and voltage (solid line).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A detailed description of preferred embodiments of the present inventionis provided below.

An electrochemical storage cell according to one embodiment of thepresent invention, which is generally designated in FIG. 1 by referencenumeral 100, includes a first electrode 102, a second electrode 104, andan electrolyte material 106 positioned therebetween and having opposingsurfaces respectively interfacing with first surfaces (unnumbered) ofthe electrodes 102 and 104. The first electrode 102 contains a currentcollector 108 with support 110, the current collector 108 being disposedon a second surface (unnumbered) of the first electrode 102 opposing thefirst surface of the first electrode 102. The second electrode 104 alsocontains a current collector 112 with support 114, the current collector112 being disposed on a second surface (unnumbered) of the secondelectrode 104 opposing the first surface of the second electrode 104.The first electrode 102 can be designated as a positive electrode(cathode), and the second electrode 104 as a negative electrode (anode).

Although not illustrated in FIG. 1, a conventional liquid electrolytecan be provided as the electrolyte material 106. In such an arrangement,the cell can further include a diaphragm or separator (not shown) toseparate the anode from the cathode. Porous or semipermeable polymericor glass materials can be selected for preparing the separator.

In order to avoid gradual oxidation of the one or more electricallyconductive polymeric electrodes and diminishment in the capacities ofthe cell or battery, the cell or battery should be closed in order toproduce a substantially oxygen- and water-free state. Thus, the cell orbattery should be enclosed in a hermetically sealed case (not shown)prepared from, for example, a metal or plastic or combination thereof.

The thickness of the first electrode 102 and the second electrode 104greatly influence the overall capacity of the cell 100. For mostpractical applications, the electrodes 102 and 104 each generally have athickness in the range of from about 10 nm to about 1 mm, and preferablyin the range of from about 0.1 μm to about 100 μm.

The current collectors 108 and 112 can be prepared from a metallicsubstrate, including such elemental metals as platinum, palladium, gold,silver, copper, titanium, and any combinations thereof, or alloys suchas stainless steel. Alternatively, the current collectors 108 and 112can be prepared from carbon, graphite, or carbon or graphite dispersedon a plastic matrix such as TEFLON, polyethylene, Kapton, orpolyvinylenedifluoride. As a further alternative, the current collectors108 and 112 can be prepared as a composite of carbon or graphitedispersed in similar plastic matrices supported by an imbedded metalmesh. The metal mesh can be elemental metals such as aluminum, titanium,gold, copper, nickel and iron, and any combinations thereof, or alloyssuch as stainless steel.

The current collectors 108 and 112 generally can have a thickness in therange of from about 100 nm to about 1 mm. In the case where carbon orgraphite films serve as one or more of the current collectors 108 and112, the film thickness of each collector 108 and 112 is generally inthe range of from about 1 μm to about 1 mm, and preferably is in therange of about 1 μm to about 10 μm. Where a metal or an alloy serves asone or more of the current collectors 108 and 112, each metal substrategenerally will be self-supporting--i.e., not requiring supports 110 and114--if the thickness of the metal or alloy substrate is at least about5 μm. Practically, the metal or alloy substrate also can have athickness in the range of from about 10 nm to about 1 mm.

The supports 110 and 114 are preferably defined by films prepared fromtetrafluoroethylene polymers (TEFLON) or polyethylene, and each can havea thickness in the range of from about 10 nm to about 1 mm, andpreferably in the range of from about 10 μm to about 500 μm.

Where an electrolyte film gel is employed as the electrolyte material106, the electrolyte film generally can have a thickness in the range ofabout 100 nm to about 1 mm, and preferably in the range of about 10 μmto 1 mm. The thickness of the film of electrolyte material 106 can becontrolled by preparing the electrolyte by spin or dip coating.

In a preferred embodiment of the invention, the electrodes 102 and 104,the current collectors 108 and 112, and the electrolyte collectivelyprovide for a thickness in the range of from about 10 μm to about 2 mm,and more preferably from about 50 μm to about 500 μm.

According to a first embodiment of the present invention, at least one,and preferably both, of the first and second electrodes 102 and 104 areprepared from at least one electrically conductive fluorophenylthiophene polymer selected from the group consisting of:

poly(3(2-fluorophenyl)thiophene);

poly(3(3-fluorophenyl)thiophene);

poly(3(2,4-difluorophenyl)thiophene);

poly(3(3,4-difluorophenyl)thiophene);

poly(3(3,5-difluorophenyl)thiophene); and

poly(3(3,4,5-trifluorophenyl)thiophene).

In a preferred embodiment of the fluorophenyl thiophene polymerelectrodes, poly(3(3,5-difluorophenyl) thiophene), which is shown inFIG. 3B, is selected as the electrically conductive polymer of thecathode 102 since it exhibits high charge capacity in the p-doped statewith good reversibility. The molecular structure of thefluorophenylthiophene monomer unit for preparingpoly(3(3,5-difluorophenyl)thiophene) is it shown in FIG. 3A.Poly(3(3,4,5-trifluorophenyl)thiophene) (FIG. 2B) is selected as theelectrically conductive polymer of the anode 104 since it exhibits ahigh charge capacity in the n-doped state with good cyclibility. Themolecular structure of the fluorophenylthiophene monomer unit forpreparing poly(3(3,4,5-trifluorophenyl)thiophene) is shown in FIG. 2A.

If only one of the electrodes 102 and 104 is prepared from theelectrically conductive polyfluorophenyl thiophene of the presentinvention, the other electrode can be selected from another knownpolymer or metallic compound.

According to a second embodiment of the present invention, at least oneof the first and second electrodes 102 and 104 are prepared from atleast one electrically conductive phenylene-thienyl based polymerselected from the group consisting of:

(i) poly(1,4-bis(2-thienyl)-benzene);

(ii) poly(1,4-bis(2-thienyl)-3-fluorophenylene);

(iii) poly(1,4-bis(2-thienyl)-3,6-difluorophenylene); and

(iv) poly(1,4-bis(2-thienyl)-2,3,5,6-tetrafluorophenylene).

In a preferred embodiment of the phenylene-thienyl based polymerelectrodes, the first electrode 102 is prepared from at least one of theforegoing phenylene-thienyl based polymers, alone or in combination withone or more of the foregoing fluorophenyl thiophene polymers, and thesecond electrode 104 is prepared from at least one of the foregoingelectrically conductive fluorophenyl thiophene polymers.

In a most preferred embodiment of the phenylene-thienyl based polymerelectrodes, poly(1,4-bis(2-thienyl)-3-fluorophenylene), which is shownin FIG. 7B (ii), is selected as the electrically conductive polymer ofthe cathode 102 since it exhibits high charge capacity in the p-dopedstate with very good reversibility. The molecular structure of the1,4-bis(2-thienyl)-3-fluoro phenylene monomer unit for preparingpoly(1,4-bis(2-thienyl)-3-fluorophenylene) is shown in FIG. 7A (ii).Poly(3(3,4,5-trifluoro phenyl)thiophene) (FIG. 2B) is selected as theelectrically conductive polymer of the anode 104 since it exhibits ahigh charge capacity in the n-doped state with good cyclibility. Themolecular structure of the fluorophenyl thiophene monomer unit forpreparing poly(3(3,4,5-trifluorophenyl)thiophene) is shown in FIG. 2A.

If only one of the electrodes 102 and 104 is prepared from theelectrically conductive phenylene-thienyl based polymers of the presentinvention, the other electrode can be selected from another knownpolymer or metallic compound.

The monomers selected to prepare the fluoro-substituted phenylthiophenepolymers of the first and second embodiments can be synthesized by, forexample, a coupling reaction between zinc complexes of variousfluoro-substituted 1-bromophenyl reagents and commercially available3-bromothiophene. This coupling reaction occurs in the presence of a[1,1-bis(diphenylphospheno)ferrocene] palladium(II) chloride("Pd(dppf)Cl₂ ") catalyst, and preferably under nonaqueous conditionsand in a dry argon atmosphere. This synthesis route provides for highisolated yields of 70% or higher.

Controlling the reaction time, temperature, and the fluoro-substituted1-bromophenyl reagent of the coupling reaction mixture determines theextent of fluorination of the phenylthiophene. For example,3(3,4,5-trifluorophenyl) thiophene, 3(3,4-difluorophenyl)thiophene, and3(3,5-difluorophenyl)thiophene are prepared by allowing the couplingreaction to proceed for about 30 minutes at about 60° C.3(2,4-difluorophenyl)thiophene, 3(2-fluorophenyl)thiophene, and3(3-fluorophenyl)thiophene were prepared by allowing the couplingreaction mixture to reflux for 10, 2, and 0.75 hours, respectively. Thecompletion of the coupling reaction was monitored by gas chromatography.Example procedures for preparing each of these fluoro-substitutedphenylthiophene polymers are set forth below.

The monomers selected to prepare the fluoro-substitutedphenylene-thienyl based polymers of the second embodiment can besynthesized by, for example, a coupling reaction between zinc complexesof various fluorosubstituted 1,4-dibromo phenylene reagents andcommercially available thiophenes. This coupling reaction occurs in thepresence of a tetrakis(triphenylphosphine) palladium [Pd(PPh₃)₄ ]catalyst, and preferably under nonaqueous conditions and in a dry argonatmosphere. This synthesis route provides for high isolated yields of40-70%.

Controlling the reaction time, temperature, and the fluoro-substituted1,4-dibromophenylene reagent of the coupling reaction mixture determinesthe extent of fluorination of the phenylene-thienyl based polymer. Forexample, 1,4 bis(2-thienyl)-benzene, 1,4bis(2-thienyl)-3-fluorophenylene, 1,4bis(2-thienyl)-2,5-difluorophenylene and 1,4bis(2-thienyl)-2,3,5,6-tetrafluorophenylene are prepared by allowing thecoupling reaction to proceed for about 24 hours at about 60-85° C. Thecompletion of the coupling reaction was monitored by thin layerchromatography and gas chromatography. Example procedures for preparingeach of these fluoro-substituted phenylene-thienyl based polymers areset forth below.

The polymeric films defining the electrodes 102 and 104 can be preparedby: (1) homopolymerizing the phenylene-thienyl based monomers and/or thefluorophenyl-substituted thiophene monomers; (2) copolymerizing blendsof two or more phenylene-thienyl based monomers and/or blends of two ormore fluorophenyl-substituted thiophene monomers; (3) copolymerizing ablend of the phenylene-thienyl based monomers with thefluorophenyl-substituted thiophene monomers; or (4) copolymerizingblends of one or more phenylene-thienyl based monomers with one or morecopolymerizable monomers and/or blends of one or morefluorophenyl-substituted thiophene monomers with one or morecopolymerizable monomers. For example, suitable copolymerizable monomersinclude those monomers containing conjugated carbon-carbon unsaturatedbonds along their backbone, such as a thiophene monomer.

Suitable techniques for conducting the homo- or co-polymerizationinclude chemical polymerization, for example in the presence ofoxidizing agents, or by electropolymerization.

According to the chemical polymerization technique, a strong oxidizingagent is added to initiate the reaction. Exemplary oxidizing agentsinclude, without limitation, Lewis acids such as ferric chloride(FeCl₃), molybdenum chloride (MoCl₅), and ruthenium chloride (RuCl₅),and oxidants such as copper perchlorate [Cu(ClO₄)₂ ]. After chemicalpolymerization is allowed to proceed in a suitable solvent, such aschloroform, the polymer can be isolated in powder form. The powder canthen be fashioned into any suitable form as the active electrodematerial. For example, the powder can be compressed into pellets, aself-supporting film, a supported sheet, or dispersed in a suitablecarrier matrix, such as an organic polymeric material. The chemicalpolymerization can take place, for example, under ambient conditions.Isolation of the powder can be achieved by filtering or evaporating thesolvent, or by other known techniques.

The preferred procedure for preparing the electrically conductingpolymers of the present invention is electropolymerization. Theelectropolymerization is usually heterogenous insofar as it involvespolymerizing the monomers on the conducting substrate to form a solidphase. Polymerization is initiated by applying an oxidizing potential tothe substrate. The oxidizing potential applied across the substrateshould be equal to or greater than the threshold polymerizationpotential of the monomer(s) in order to initiate polymerization. Asreferred to herein, the threshold polymerization potential is athreshold potential at which a current begins to flow across thepolymerizable solution and the monomers begin to polymerize on thesubstrate. An external circuit with a current sensing meter can beutilized to determine when the current begins to flow. Alternatively,the threshold polymerization potential can be visually detected byformation of the polymer on the substrate, although some degree ofpolymerization must occur before visual detection is possible.

The polymerization potentials of the monomers of the present inventionwere found to be accessible in solvents such as propylene carbonate,resulting in the deposition of high quality films. The polymers can alsobe formed as powders, which can then be compacted to prepare theelectrodes.

The temperature at which the electropolymerization is carried out isgenerally about room temperature, although temperatures ranging about20° C. higher and 20° C. lower than room temperature can be employed.The electropolymerization can be carried out at atmospheric pressure.

Suitable substrates for the electropolymerization of thefluoro-substituted phenylene-thienyl based monomers and thefluorophenyl-substituted thiophene monomers include, by way of example,platinum, palladium, gold, silver, titanium, copper, stainless steel,and any combinations thereof. Carbon, graphite, conducting tin oxide,and carbon-doped polyethylene can also be selected as the substrate forthe electropolymerization. These substrates can serve as the currentcollectors 108 and 112 of the cell 100; accordingly,electropolymerization can obviate the need for an additional preparatorystep of transferring the polymeric electrodes 102 and 104 to the currentcollectors 108 and 112, respectively.

In addition, if desirable, conventional additives such as graphite,carbon black, acetylene black, metal powder, or carbon fiber may beincorporated in the polymeric electrolyte of the present invention,although the electrodes are preferably prepared without such additives.

These secondary batteries may be either initially assembled in a chargedstate, or initially assembled in an uncharged state, and subsequentlyconverted in situ to such charged state by means of electrochemicaldoping. Preferably, the cells are assembled in the fully neutralizedstate to ensure that the electrolyte concentration in the gel does notexceed the solubility limit in the fully discharged state duringcycling, that is, to ensure that the electrolyte salt does notprecipitate out during discharge of the cell.

For example, the electrochemical doping technique can be applied bycharging the electrochemical cell 100 by connecting a direct current(DC) voltage source to the electrodes 102 and 104. In particular, thepositive potential of the voltage source is applied to the polymericelectrode selected as the cathode, and a negative potential is connectedto the polymeric electrode selected as the anode. The application of thepositive potential to the neutral polymer selected as the cathodeeffects an increase in the oxidation state of the polymer by electrontransfer from the polymer, imparting a net positive charge to thepolymer. Consequently, the polymer forming the cathode attracts anionsfrom the electrolyte 106 as counter ions to maintain the electricalneutrality in the polymer. On the other hand, application of thenegative potential to the neutral polymer selected as the anode effectsa decrease in the oxidation state of the polymer by electron transfer tothe polymer, imparting a net negative charge to the polymer.Consequently, the polymer forming the anode attracts cations from theelectrolyte 106 as counter ions to maintain the electrical neutrality inthe polymer.

The doping level can be controlled by measuring the quantity ofelectricity flowing during charging of the cell or by measuring thevoltage. Doping may be carried out under constant current or constantvoltage conditions or under a varying current or varying voltagecondition. The doping current, voltage, and time vary depending on thekind, bulk density, and area of the polymeric electrode, the electrolytesalt and solvent selected, and the desired temperature.

Alternatively, the polymers can initially be chemically doped withdopant species.

A practical charge storage device utilizing conducting polymers for bothanode and cathode requires not only the selection of two materials thatcan be n-doped and p-doped, respectively, to provide adequate chargecapacities, but also an electrolyte that is compatible with thesematerials. That is, the electrolyte salt and solvent selected shouldallow a sufficiently large potential range to attain the polymerizationpotential, as well as the full n-doped and p-doped states, of thepolymers.

According to a preferred embodiment of the present invention, theelectrolyte selected is an ionically conducting polymer gel. Exemplarycations for preparing the electrolyte salts that can be employed inaccordance with the present invention include, without limitation,cations of tetraalkyl ammonium, sodium, lithium, potassium, silver, andmagnesium. Exemplary anions for preparing the electrolyte salts suitablefor the present invention include, without limitation, tetrafluoroborate(BF₄ ⁻), hexafluoroarsenate (AsF₆ ⁻) hexafluorophosphate (PF₆ ⁻),hexafluoroantimonate (SbF₆ ⁻), trifluoromethane sulfonate (CF₃ SO₃ ⁻),bis-trifluoro methylsulfonyl imide or "imid salt" ((CF₃ SO₂)₂ N⁻),cyclic imid salt, perchlorate (ClO₄ ⁻), thiocyanate (SCN⁻), and iodide(I⁻).

For example, among the salts that can be practiced with the presentinvention are the following: tetrabutylammonium hexafluoro phosphate,lithium tetrafluoroborate, tetraethylammonium tetrafluoborate,tetrabutylammonium tetrafluoroborate, lithium perchlorate,tetrabutylammonium perchlorate, tetraethyl ammonium perchlorate,tetramethyl ammonium trifluoromethane sulfonate, and tetrabutylammoniumhexafluorophosphate. Preferably, tetrabutylammonium tetrafluoroborate isselected as the electrolyte salt, since this salt has high solubilityand electrochemical stability and provides good cycling efficiency forthe conducting polymers.

Suitable electrolyte solvents include, by way of example, the following:ethers, such as tetrahydrofuran (THF), dimethoxyethane, dioxolane,2-methyltetrahydrofuran, and diethyl ether; esters, such asT-butyrolactone, propylene carbonate, ethylene carbonate, dimethylcarbonate, diethyl carbonate, dibutyl carbonate, methyl formate, ethylformate, ethyl acetate, and methyl acetate; nitrogen-containingcompounds such as nitrobenzene, nitromethane, acetonitrile,benzonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, nitroethane,and propylonitrile; sulfur-containing organic compounds, such asdimethylsulfoxide and sulfolane; and others such as dichloromethane andacetone. Preferably, propylene carbonate or sulfolane is selected as theelectrolyte solvent.

Polymer gels are defined herein as mixed-phase materials with good ionicconductivity that can be solution cast into thin flexible films. Theability to solution cast the gel prior to gelation onto the electrodesensures good contact between the polymer electrodes and the electrolytefilm. Such casting can be performed by spin or dip coating, as well asother techniques known in the art. Optionally, the gel can be formed ona temporary substrate and transferred to the electrodes. Where theelectrolyte is to prepared as a gelled film, suitable gelling agentsthat can be employed include: poly(ethyleneoxide), poly(propyleneoxide), poly(vinylidene dichloride), poly(vinylsulfone),poly(vinylidenedifluoride), poly(2,2-dimethyltrimethylenecarbonate),poly(acrylonitrile), poly(vinylchloride), poly(ethyleneglycol),poly(propylene glycol), poly(tetrahydrofuran), poly(dioxolane), poly(siloxanes), poly(ethoxyethoxyethoxyvinylether), poly (phosphazene),poly(methylmethaacrylate), poly(styrene),poly[bis(methoxyethoxy)phosphazene], poly(acrylic acid),poly(methylacrylate), poly(vinylformal), poly(vinylene carbonate),poly(vinylacetate), poly(vinylpyrrolidone), poly(acrylamide),poly(ethoxy(proyleneglycol)acrylate), and others. Preferably,poly(acrylonitrile) is selected as the gelling agent.

The concentration of the electrolyte salt in the solvent depends uponthe electrodes selected, the charging and discharging conditions, theoperating temperature, and the specific electrolyte salt and solventselected, and, therefore, is generally not defined. It is ordinarilypreferred, however, that the concentration be about 0.1 to about 3M, andmost preferably about 1.0M.

The charging of the electrodes is described above. In operation of theelectrochemical cell, the electrodes are reversibly discharged.

For example, the cell reactions during discharge of a cell containing apoly(3(3,4,5-trifluorophenyl)thiophene) anode,poly(3(3,5-difluorophenyl)thiophene) cathode, and tetrabutyl ammoniumtetrafluoroborate in propylene carbonate electrolyte are as follows:

(1) anode:

poly(3(3,4,5-trifluorophenyl)thiophene)_(n) ⁻ ·TBA⁺ →

poly(3(3,4,5-trifluorophenyl)thiophene)⁰ +TBA⁺ +e⁻

(2) cathode:

poly(3(3,5 difluorophenyl)thiophene)_(m) ⁺ ·BF₄ ⁻ +e⁻ →

poly(3(3,5 difluorophenyl)thiophene)⁰ +BF₄ ⁻

wherein TBA⁺ represents a tetrafluoroborate cation, BF₄ represents atetrabutylammonium anion, and n and m denote the number of monomerunits.

As a further example, the cell reactions during discharge of a cellcontaining a poly(3(3,4,5-trifluorophenyl)thiophene) anode,1,4-bis(2-thienyl)-3-fluorophenylene cathode, and tetrabutyl ammoniumtetrafluoroborate in propylene carbonate electrolyte are as follows:

(1) anode:

poly(3(3,4,5-trifluorophenyl)thiophene)_(n) ⁻ ·TBA⁺ →

poly(3(3,4,5-trifluorophenyl)thiophene)⁰ +TBA⁺ +e⁻

(2) cathode:

poly(1,4-bis(2-thienyl)-3-fluorophenylene)_(m) ⁺ ·BF₄ ⁻ +e⁻ →

poly(1,4-bis(2-thienyl)-3-fluorophenylene)⁰ +BF₄ ⁻

wherein TBA+ represents a tetrafluoroborate cation, BF₄ ⁻ represents atetrabutylammonium anion, and n and m denote the number of monomerunits.

As evident from these equations, in the charged state both electrodesare fully doped so that during discharge, the polymers are neutralizedand the ion concentration in the electrolyte polymer gel increases asthe charge compensating TBA⁺ and BF₄ ⁻ counter ions are ejected from theelectrodes. Consequently, in order to optimize the cell electrochemicalproperties the minimum thickness of the gel film is determined by thesolubility limit of the salt in the gel.

The electrochemical properties of the fluorophenyl thiophene polymers ofthe present invention, as well as those ofpoly(3(4-fluorophenyl)thiophene) as a comparative example, aresummarized below in Table I. The electrochemical properties of thephenylene-thienyl based polymers of the present invention, as well asthose of poly(3(3,4,5-trifluorophenyl)thiophene) as a comparativeexample, are summarized below in Table II.

                                      TABLE I                                     __________________________________________________________________________                                Anode                                                                              Cathode                                              Anodic                                                                             Cathodic                                                                           Anode                                                                              Cathode                                                                            Average                                                                            Average                                              Charge                                                                             Charge                                                                             Charge                                                                             Charge                                                                             stability                                                                          stability                                    Polyfluorophenyl-                                                                     Capacity                                                                           Capacity                                                                           Density                                                                            Density                                                                            per cycle                                                                          per cycle                                    thiophenes                                                                            (e/mu).sup.a                                                                       (e/mu).sup.a                                                                       (mAh/g).sup.b                                                                      (mAh/g).sup.b                                                                      (%)  (%)                                          __________________________________________________________________________    poly(3(3,4,5-                                                                         0.26 0.23 32.1 28.4 99.53                                                                              99.90                                        trifluorophenyl)                                                              thiophene)                                                                    poly(3(3,5-                                                                           0.26 0.21 35.2 29.0 98.37                                                                              99.92                                        difluorophenyl)                                                               thiophene)                                                                    poly(3(3,4-                                                                           0.16 0.21 21.3 28.5 99.85                                                                              99.88                                        difluorophenyl)                                                               thiophene)                                                                    poly(3(2,4-                                                                           0.18 0.17 23.9 23.5 99.76                                                                              99.91                                        difluorophenyl                                                                thiophene)                                                                    poly(3(2-                                                                             0.15 0.18 22.6 26.8 99.80                                                                              99.94                                        fluorophenyl)                                                                 thiophene)                                                                    poly(3(3-                                                                             0.18 0.18 26.8 26.7 99.88                                                                              99.87                                        fluorophenyl)                                                                 thiophene)                                                                    poly(3(4-                                                                             0.10 0.20 14.8 30.6 99.88                                                                              99.87                                        fluorophenyl)                                                                 thiophene)                                                                    __________________________________________________________________________            Electro-                                                                      polymerization                                                                       Oxidation Peak                                                                       Reduction Peak                                                                       Negative                                                                           Positive                                            Potentials of                                                                        Potentials (V).sup.c                                                                 Potentials (V).sup.c                                                                 Voltage                                                                            Voltage                                     Polyfluorophenyl-                                                                     the Monomers                                                                         of Polymers                                                                          of Polymers                                                                          Limit                                                                              Limit                                       thiophenes                                                                            (V).sup.c                                                                            (n-dopings).sup.d                                                                    (p-doping).sup.d                                                                     (V).sup.c,d                                                                        (V).sup.c,d                                 __________________________________________________________________________    poly(3(3,4,5-                                                                         1.15   -1.77  0.58   -2.08                                                                              0.88                                        trifluorophenyl)                                                              thiophene)                                                                    poly(3(3,5-                                                                           1.15   -1.87  0.63   -2.13                                                                              0.88                                        difluorophenyl)                                                               thiophene)                                                                    poly(3(3,4-                                                                           1.06   -1.85  0.56   -2.10                                                                              0.80                                        difluorophenyl)                                                               thiophene)                                                                    poly(3(2,4-                                                                           1.10   -1.83  0.54   -2.10                                                                              0.80                                        difluorophenyl)                                                               thiophene)                                                                    poly(3(2-                                                                             1.06   -1.88  0.55   -2.10                                                                              0.80                                        fluorophenyl)                                                                 thiophene)                                                                    poly(3(3-                                                                             0.98   -1.99  0.52   -2.10                                                                              0.80                                        fluorophenyl)                                                                 thiophene)                                                                    poly(3(4-                                                                             0.96   -1.93  0.54   -2.10                                                                              0.80                                        fluorophenyl)                                                                 thiophene)                                                                    __________________________________________________________________________     .sup.a electron/monomer unit,                                                 .sup.b first cycle                                                            .sup.c vs. Ag.sup.+ /Ag,                                                      .sup.d first cycle                                                       

                                      TABLE II                                    __________________________________________________________________________                                   Anode                                                                              Cathode                                              Anodic                                                                             Cathodic                                                                           Anode                                                                              Cathode                                                                            Average                                                                            Average                                              Charge                                                                             Charge                                                                             Charge                                                                             Charge                                                                             Stability                                                                          Stability                                 Phenylene- Capacity                                                                           Capacity                                                                           Density                                                                            Density                                                                            per Cycle                                                                          per Cycle                                 thienyl based polymers                                                                   (e/mu).sup.a                                                                       (e/mu).sup.a                                                                       (mAh/g).sup.b                                                                      (mAh/g).sup.b                                                                      (%)  (%)                                       __________________________________________________________________________    poly(1,4-bis(2-thienyl)-                                                                 0.17 0.44 17.77                                                                              44.79                                                                              99.64                                                                              >99.99                                    3-fluorophenylene)                                                            poly(1,4-bis(2-thienyl)-                                                                 0.36 0.41 34.58                                                                              39.59                                                                              99.14                                                                              99.54                                     3,6-difluorophenylene)                                                        poly(1,4-bis(2-thienyl)-                                                                 0.30 0.60  6.50                                                                              28.00                                                                              99.83                                                                              99.60                                     2,3,5,6-tetra-                                                                fluorophenylene)                                                              poly(1,4-bis(2-                                                                          0.13 0.64 13.81                                                                              71.02                                                                              99.18                                                                              99.74                                     thienyl)-benzene)                                                             poly(3(3,4,5-trifluoro-                                                                  0.26 0.23 32.1 28.4 99.53                                                                              99.90                                     phenyl)thiophene)                                                             __________________________________________________________________________                        Electro-                                                                      polymerization                                                                Potentials of                                                                        Negative                                                                             Positive                                    Phenylene-          the Monomers                                                                         Voltage Limit                                                                        Voltage Limit                               thienyl based polymers                                                                   Monomer  (V).sup.c                                                                            (V).sup.c                                                                            Limit (V).sup.c                             __________________________________________________________________________    poly(1,4-bis(2-thienyl)-                                                                 1,4-bis(2-thienyl)-                                                                    0.675  -2.08  1.15                                        3-fluorophenylene)                                                                       3-fluoro-phenylene                                                 poly(1,4-bis(2-thienyl)-                                                                 1,4-bis(2-thienyl)-                                                                    0.785  -2.34  1.26                                        3,6-difluorophenylene)                                                                   3,6-difluoro-                                                                 phenylene                                                          poly(1,4-bis(2-thienyl)-                                                                 1,4-bis(2-thienyl)-                                                                    1.110  -2.16  1.34                                        2,3,5,6-tetra-                                                                           2,3,5,6-tetrafluoro                                                fluorophenylene)                                                                         phenylene                                                          poly(1,4-bis(2-                                                                          1,4-bis(2-thienyl)-                                                                    0.575  -2.4   1.30                                        thienyl)-benzene)                                                                        benzene                                                            poly(3(3,4,5-trifluoro-                                                                  3(3,4,5-trifluoro-                                                                     1.1    -2.08  0.88                                        phenyl)thiophene)                                                                        phenyl)thiophene                                                   __________________________________________________________________________     .sup.a electron/monomer unit                                                  .sup.b first cycle                                                            .sup.c vs. Ferrocene.sup.+ /Ferrocene                                    

As presented in Table I, each of the polyfluorophenyl thiophene polymersof the present invention exhibited a remarkably superior anodic chargecapacity over poly(3(4-fluorophenyl)thiophene).Poly(3(3,4,5-trifluorophenyl) thiophene) exhibited the highest chargecapacity in the n-doped state, together with excellent electrochemicalstability. Thus, in a first preferred embodiment of the invention,poly(3(3,4,5-trifluorophenyl)thiophene) is selected as the electricallyconductive polymer of the anode 104. On the other hand,poly(3(3,5-difluorophenyl)thiophene) exhibited very high charge capacityand very high electrochemical stability in the p-doped state, and,therefore, is selected as the electrically conductive polymer of thecathode 102.

As presented in TABLE II, poly(1,4-bis(2-thienyl)3-fluoro phenylene) andpoly(1,4 bis(2-thienyl)-benzene) exhibited a high cathodic chargecapacity compared to the polyfluorophenyl thiophenes presented in TableI. Poly(1,4-bis(2-thienyl)3-fluorophenylene) exhibited the bestperformance as it presents high charge capacity in the p-doped statewith excellent electrochemical stability. Thus, in a second and mostpreferred embodiment of the invention, poly(1,4-bis(2-thienyl)-3-fluorophenylene) is selected as the electricallyconductive polymer of the cathode 102. On the other hand,poly(3,(3,4,5-trifluorophenyl)thiophene), from the group ofpolyfluorophenyl thiophenes, exhibited very high charge capacity andvery high electrochemical stability in the n-doped state, and,therefore, is selected as the electrically conductive polymer of theanode 104.

The following non-limiting examples serve to explain the preparation ofthe fluoro-substituted phenylthiophene monomers and polymers, thepreparation and characteristics of an electrochemical cell containingsuch polymers, the preparation of the fluoro-substitutedphenylene-thienyl based monomers and polymers, and the preparation andcharacteristics of an electrochemical cell containing such polymers, inmore detail.

EXAMPLES Example A

(1) Synthesis of fluorophenyl thiophene monomers

(a) Synthesis of 3(3,4,5-trifluorophenyl)thiophene

In a first three-necked round-bottom flask (100 ml), metallic magnesium(52 mmol) (product #25411-8, manufactured by Aldrich Chemical) was flamedried in an argon atmosphere for 3 to 4 minutes. Upon cooling under theargon atmosphere, 50 ml of freshly dried tetrahydrofuran (product #T397-4, manufactured by Fisher Scientific) was previously distilled froma sodium/bentophenone mixture and directly drawn into the flask from thedistillation head. Into this mixture of magnesium and tetrahydrofuranwas added 1-bromo-3,4,5-trifluorobenzene (26 mmol) (product #33084-1,manufactured by Aldrich Chemical), which remained in an argon atmosphereand was stirred. After the mixture was warmed to about 40° C. (afterabout 3 to 4 minutes), the flask was cooled (e.g., via an ice bath) andcontinuously stirred for 2 hours to form a magnesium complex. Anhydrouszinc chloride (ZnCl₂) (31 mmol) (product #20808-6, manufactured byAldrich Chemical) previously dried at 160° C. under vacuum conditionswas weighed in the dry box, and added to the magnesium complex at roomtemperature. After stirring for 30 minutes, the zinc complex suspensionwas transferred (e.g., via Teflon tubing) under argon pressure to asecond three-necked round-bottomed flask (250 mL) containing a solutionof 3-bromothiophene (21 mmol) (product #10622-4, manufactured by AldrichChemical) and Pd(dppf)Cl₂ catalyst (product #37967-0, manufactured byAldrich Chemical). This coupling reaction mixture was then heated (e.g.,via an oil bath) for 0.5 hour with continuous stirring at 60° C.

The completion of the coupling reaction was monitored by gaschromatography using aliquot of reaction mixture after the work-updescribed below. When most of the 3-bromothiophene was consumed asdetermined by gas chromatography, the crude reaction mixture wasworked-up as follows: The reaction mixture was quenched with 10 mL of 5wt. % aqueous sulfuric acid at room temperature. After evaporating thetetrahydrofuran using a rotary evaporator, dichloromethane (40 mL) andwater (40 mL) were added to the crude reaction mixture and extracted.The organic layer was washed three times with water, and then was driedover anhydrous sodium sulfate, followed by evaporation. An oily brownliquid resulted. Purification of the crude product was carried out bycolumn chromatography using silica gel (stationary phase) and n-pentane(as an eluent). The crude product was initially absorbed on the silicagel (about 2 to 3 grams) and charged on the column. The net weight ratioof crude product to the silica gel stationary phase was about 50:1.Chromatographic resolution was checked periodically by using a silicagel thin layer chromatography plate (product #Z12278-5, manufactured byAldrich Chemical) and n-pentane as the eluent.3,4,5-trifluorophenylthiophene was further purified by crystallizationfrom n-pentane at 0° C. to obtain a 98 to 99% pure product.

(b) Synthesis of 3(3,4-difluorophenyl)thiophene

The same procedures set forth above in Example A(1)(a) for synthesizing3(3,4,5-trifluorophenyl)thiophene were followed, with the exception that1-bromo-3,4-difluorobenzene was substituted for1-bromo-3,4,5-trifluorobenzene as the 1-bromo-substituted fluorobenzene.

(c) Synthesis of 3(3,5-difluorophenyl)thiophene

The same procedures set forth above in Example A(1)(a) for synthesizing3(3,4,5-trifluorophenyl)thiophene were followed, with the exception that1-bromo-3,5-difluorobenzene was substituted for1-bromo-3,4,5-trifluorobenzene as the 1-bromo-substituted fluorobenzene.

(d) Synthesis of 3(2,4-difluorophenyl)thiophene

The same procedures set forth above in Example A(1)(a) for synthesizing3(3,4,5-trifluorophenyl)thiophene were followed, with the exception that1-bromo-2,4-difluorobenzene was substituted for1-bromo-3,4,5-trifluorobenzene as the 1-bromo-substituted fluorobenzene,and the coupling reaction mixture was heated to reflux in an oil bathfor 10 hours with stirring at 80° C. (as opposed to being heated in anoil bath for 0.5 hour with periodically stirring). No furtherpurification by recrystallization was required to obtain a 97 to 98%pure product.

(e) Synthesis of 3(2-difluorophenyl)thiophene

The same procedures set forth above in Example A(1)(d) for synthesizing3(2,4-difluorophenyl)thiophene were followed, with the exception that1-bromo-2-fluorobenzene was substituted for 1-bromo-2,4-difluorobenzeneas the 1-bromosubstituted fluorobenzene, and the coupling reactionmixture was heated to reflux in an oil bath for 2 hours with stirring at80° C. No further purification by recrystallization was required toobtain a 97 to 98% pure product.

(f) Synthesis of 3(3-difluorophenyl)thiophene

The same procedures set forth above in Example A(1)(d) for synthesizing3(2,4-difluorophenyl)thiophene were followed, with the exception that1-bromo-3-fluorobenzene was substituted for 1-bromo-2,4-difluorobenzeneas the 1-bromosubstituted fluorobenzene, and the coupling reactionmixture was heated to reflux in an oil bath for 0.75 hours with stirringat 80° C.

(2) Preparation of an electrolyte gel

An illustrative polymer gel was prepared by heating 3.7 wt %poly(acrylonitrile) as a gelling agent having a molecular weight ofabout 150,000 g/mol in a propylene carbonate solvent containing 0.25Mtetrabutylammonium tetrafluoroborate salt (Sachem electrometric gradeprepared by dehydration at 130° C. under dynamic vacuum for 48 hours) at141° C. FIG. 5 shows the conductivity of the resulting gel as a functionof temperature, wherein the abscissa is the reciprocal of temperature(K⁻¹), and the ordinate is conductivity (S/cm). The conductivity of thegel was essentially similar to that of liquid phase organic electrolytesand remained relatively high even at low temperatures. In contrast, theconductivity of single phase solid electrolytes, such as poly(ethyleneoxide)-based electrolytes, decreased rapidly below the glass transitiontemperatures of the polymer.

(3) Preparation of an all-polymer battery

An all-polymer battery incorporatingpoly(3(3,4,5-trifluorophenyl)thiophene) as the anode andpoly(3(3,5-difluorophenyl)thiophene) as the cathode, and the electrolyteof Example A(2) was prepared as follows.

The polymeric electrodes for the all-polymer battery wereelectrochemically deposited from a solution of 0.1M of monomers. A totalof 3 C/cm² of each monomer (corresponding to 2.8 mg/cm² ofpoly(3(3,4,5-trifluorophenyl)thiophene) and 2.6 mg/cm² ofpoly(3,(3,5-difluorophenyl)thiophene)) was deposited on a 25 μm thickgraphite-coated TEFLON film resulting in thin and flexible electrodeseach having a thickness and surface areas of about 10 μm and about 9cm², respectively, with no metallic components. Under these depositionconditions the films were smooth and continuous with a nodular structurecharacteristic of many conducting polymers.

Electrochemical cells were then assembled in the neutralized state byshifting the potential of the polymeric electrode films into a regionsuch that the polymeric electrode films were undoped and storing thepolymeric electrode films in anhydrous propylene carbonate.

FIG. 4 shows a cyclic voltammogram for n-doping/undoping of thepoly(3(3,4,5-trifluorophenyl)thiophene) and p-doping/undoping ofpoly(3(3,5 difluorophenyl)thiophene) in a liquid electrolyte. Thevoltammogram illustrates the highly reversible doping process associatedwith these polymers. In acquiring the voltammogram, a scan rate of 25mV/s was used to ensure that the films were fully doped and undopedduring successive scans. All potentials are referenced to the Ag⁺ /Agredox couple in the same solution.

The relevant properties of the two polymers are summarized below inTable III:

                  TABLE III                                                       ______________________________________                                                              poly(3(3,4,5-                                                      poly(3,5-difluoro-                                                                       trifluorophenyl)                                                   phenyl thiophene                                                                         thiophene)                                                         (p-doping: cathode)                                                                      (n-doping: anode)                                       ______________________________________                                        doping level 0.21         0.26                                                (electrons/-                                                                  monomer unit)                                                                 charge density                                                                             29.0         32.1                                                (mAh/g)                                                                       average stability                                                                          99.92        99.53                                               per cycle (%)                                                                 electro-     1.15         1.15                                                polymerization                                                                potential (V)                                                                 potential of fully                                                                         0.88         -2.08                                               doped state                                                                   potential of the                                                                           0.56         -1.79                                               neutralization                                                                peak                                                                          ______________________________________                                    

The electrode materials of these examples exhibited good charge capacityand cyclibility. The potential difference between the fully p-doped andfully n-doped states of the two polymers is 2.96 V, corresponding to themaximum expected open circuit voltage of a fully charged cellconstructed from these two materials. From the potential differencebetween the current peaks associated with neutralization of both then-doped and p-doped states, the plateau voltage during discharge isexpected to be about 2.35 V. The average charge capacities, based on themass of the dry, neutralized polymer, were 32.1 mAh/g for thepoly(3(3,4,5-trifluorophenyl) thiophene) and 29.0 mAh/g for thepoly(3(3,5-difluorophenyl) thiophene). The cycling efficiency for thepoly(3(3,4,5-trifluorophenyl)thiophene) was 99.53% per cycle averagedover 100 cycles. This corresponds to a total loss of capacity of 47%over 100 cycles and is significantly better than other n-doped polymers.The loss of capacity represents an extreme case since the films wouldnot be expected to be completely charged and discharged in normalbattery usage.

These cells exhibited specific charge capacities between 9.5 to 11.5mAh/g and energy densities of 22.8 to 27.6 mWh/g, based on the totalactive mass of the anode and cathode. The average cycling efficiency,calculated from the charge retained after a maximum of 150 cycles, was99.1W. As shown in FIGS. 6A and 6B the discharge curve exhibits anextended region at voltages between 2.2 and 2.7 V, consistent with thevalue expected from the cyclic voltammograms of the two polymers. Theseoperating voltages are higher than for traditional aqueous batteries andare comparable to lithium battery systems such as Li/MOS₂ and Li/TiS₂ aswell as some lithium intercalation systems. Although the specific chargecapacities reported here are not as large as for lithium batteries, thecells nonetheless are of practical interest given the good cyclibility.

The above-described performance of the electrochemical cells wascharacterized by recording multiple charge/discharge cycles of severalsample cells. The procedure for charging and discharging was as follows.The cells were charged at constant current of 25 μA/cm² up to 2.8 V andheld at this voltage until the current dropped to 5 μA/cm². At thispoint, the cells were discharged at a constant current of 25 μA/cm²until the cell voltage dropped to 1 V. This procedure corresponds toalmost 100% depth of discharge. The inset of FIG. 6B shows both therelations between charge time and voltage (dotted line) and dischargetime and voltage for batteries prepared in accordance with this ExampleA (solid line).

Example B

(1) Synthesis of phenylene-thienyl based monomers

(a) Synthesis of 1,4-bis(2-thienyl)-benzene

A three-necked round-bottom flask (250 ml) was flame dried in an argonatmosphere for 10 to 15 minutes. Upon cooling under the argonatmosphere, 50 ml of freshly dried tetrahydrofuran (product #T 397-4,manufactured by Fisher Scientific) was previously distilled from asodium/benzophenone mixture and directly drawn into the flask from thedistillation head. A measured amount of thiophene (94 mmol) was added toTHF in the reaction flask. Into this solution of thiophene andtetrahydrofuran at 0° C. was gradually added n-butyllithium (94 mmol)(product #23070-7, manufactured by Aldrich Chemical), which remained inan argon atmosphere and was stirred. After stirring for 3 hours at60-65° C., a tetrahydrofuran solution of anhydrous zinc chloride (ZnCl₂)(94 mmol) (product #20808-6, manufactured by Aldrich Chemical)previously dried at 160° C. under vacuum conditions and weighed in thedry box, was gradually added to the lithium complex at room temperature.After stirring for 45 minutes, the zinc complex suspension wastransferred (e.g., via Teflon tubing) under argon pressure to a secondthree-necked round-bottomed flask (500 mL) containing a solution of1,4-dibromobenzene (31 mmol) (product #D3902-9, manufactured by AldrichChemical) and Pd(PPh₃)₄ catalyst (product #0953, manufactured byLancaster Synthesis, Inc.). This coupling reaction mixture was thenheated (e.g., via an oil bath) for 24 hours with continuous stirring at60-65° C.

The completion of the coupling reaction was monitored by thin layerchromatography and gas chromatography using aliquot of reaction mixtureafter the work-up described below. When most of the 1,4-dibromobenzenewas consumed as determined by gas chromatography, the crude reactionmixture was worked-up as follows: The reaction mixture was quenched with10 mL of 5 wt. % aqueous sulfuric acid at room temperature. Afterevaporating the tetrahydrofuran using a rotary evaporator,dichloromethane (40 ml) and water (40 mL) were added to the crudereaction mixture and extracted. The organic layer was washed three timeswith water, and then was dried over anhydrous sodium sulfate, followedby evaporation. A yellowish solid resulted. Purification of the crudeproduct was carried out by column chromatography using silica gel(stationary phase) and n-pentane/dichloromethane mixture (as an eluent).The crude product was initially absorbed on the silica gel (about 4 to 5grams) and charged on the column. The net weight ratio of crude productto the silica gel stationary phase was about 50:1. Chromatographicresolution was checked periodically by using a silica gel thin layerchromatography plate (product #Z12278-5, manufactured by AldrichChemical) and n-pentane as the eluent. 1,4-bis(2-thienyl)-benzeneobtained was 98 to 99% pure product.

(b) Synthesis of 1,4-bis(2-thienyl)-3-fluorophenylene

The same procedures set forth above in Example B(1)(a) for synthesizing1,4-bis(2-thienyl)-benzene were followed, with the exception that1,4-dibromo-3-fluorobenzene was substituted for 1,4-dibromobenzene asthe 1,4-dibromosubstituted fluorobenzene.

(c) Synthesis of 1,4-bis(2-thienyl)2,5-difluorophenylene

The same procedures set forth above in Example B(1)(a) for synthesizing1,4-bis(2-thienyl)-benzene were followed, with the exception that1,4-dibromo-2,5-difluorobenzene was substituted for 1,4-dibromobenzeneas the 1,4-dibromosubstituted fluorobenzene.

(d) Synthesis of 1,4-bis(2-thienyl)2,3,5,6-tetrafluorophenylene

The same procedures set forth above in Example B(1)(a) for synthesizing1,4-bis(2-thienyl)-benzene were followed, with the exception that1,4-dibromo-2,3,5,6-tetrafluorobenzene was substituted for1,4-dibromobenzene as the 1,4-dibromo-substituted fluorobenzene. Thecoupling reaction mixture was heated to reflux in an oil bath for 24hours with stirring at 80° C. (as opposed to being heated in an oil bathfor 24 hours at 60° C.). The product obtained was 97 to 98% pure.

(2) Preparation of an electrolyte gel

An illustrative polymer gel was prepared by heating in one container5.13 wt % poly(acrylonitrile) as a gelling agent having a molecularweight of about 150,000 g/mol in a propylene carbonate solvent at140-160° C. In another container is added propylene carbonate containingtetrabutylammonium tetrafluoroborate salt (Sachem electrometric gradeprepared by dehydration at 130° C. under dynamic vacuum for 48 hours) at140-160° C. The salt concentration was calculated as to obtain a totalof 1M of tetrabutylammonium tetrafluoroborate salt in the final mixtureof the poly(acrylonitrile) in propylene carbonate solution with the saltin propylene carbonate solution. After mixing the contents of the twocontainers together a clear viscous solution of the gel was spread onglass plates and left to set for one day. An alternative procedure is tospread the hot gel between two glass plates and imbed glass fiber filterpaper in the gel to impart better mechanical properties to the final gelfilm.

(3) Preparation of an all-polymer battery

An all-polymer battery incorporatingpoly(3(3,4,5-trifluorophenyl)thiophene) as the anode and poly(1,4-bis(2-thienyl)- 3-fluorophenylene) as the cathode, and the electrolyte ofExample B(2) was prepared as follows.

The polymeric electrodes for the all-polymer battery wereelectrochemically deposited from a solution of 0.1M of monomers to atotal charge of 3.0-4.5 C/cm² (corresponding to 2.8-4.1 mg/cm² ofpoly(3(3,4,5-trifluorophenyl)thiophene) and 1.99-2.3 mg/cm² of1,4-bis(2-thienyl)-3-fluorophenylene). As a result, each polymer wasdeposited on a 1.25-1.4 μm thick graphite-coated TEFLON film (125 μm) orcarbon loaded poly(ethylene)/gold plated stainless steel mesh compositeresulting in thin and flexible electrodes each having a thickness andsurface areas of about 2 mm and about 9 cm², respectively.

Electrochemical cells were then assembled in the neutralized state byshifting the potential of the polymeric electrode films into a regionsuch that the polymeric electrode films were undoped and storing thepolymeric electrode films in anhydrous propylene carbonate.

FIG. 8 shows a cyclic voltammogram for the n-doping/undoping of thepoly(3(3,4,5-trifluorophenyl) thiophene) and p-doping/undoping of1,4-bis(2-thienyl)3-fluorophenylene in 0.25M tetrabutylammoniumtetrafluoroborate in propylene carbonate. The voltammogram illustratesthe highly reversible doping process associated with these polymers. Inacquiring the voltammogram, a scan rate of 25 mV/s was used to ensurethat the films were fully doped and undoped during successive scans. Allpotentials are referenced to the Ferrocenium/Ferrocene redox couple inthe same solution.

The relevant properties of the two polymers are summarized below inTable IV:

                  TABLE IV                                                        ______________________________________                                                              poly(3(3,4,5-                                                      1,4-bis(2-thienyl)-                                                                      trifluorophenyl)                                                   3-fluorophenylene                                                                        thiophene)                                                         (p-doping: cathode)                                                                      (n-doping: anode)                                       ______________________________________                                        doping level 0.44         0.26                                                (electrons/-                                                                  monomer unit)                                                                 charge density                                                                             44.8         32.1                                                (mAh/g)                                                                       average stability                                                                          >99.99       99.53                                               per cycle (%)                                                                 electro-     0.675        1.15                                                polymerization                                                                potential (V)                                                                 potential of 1.15         -2.08                                               fully doped state                                                             potential of the                                                                           0.8          -1.79                                               neutralization                                                                peak                                                                          ______________________________________                                    

The electrode materials of these examples exhibited good charge capacityand cyclibility. The potential difference between the fully p-doped andfully n-doped states of the two polymers is 3.25 V, corresponding to themaximum expected open circuit voltage of a fully charged cellconstructed from these two materials. From the potential differencebetween the current peaks associated with neutralization of both then-doped and p-doped states, the plateau voltage during discharge isexpected to be about 2.5 V. The average charge capacities, based on themass of the dry, neutralized polymers, were 32.1 mAh/g for thepoly(3(3,4,5-trifluorophenyl)thiophene) and 44.8 mAh/g for thepoly(1,4-bis (2-thienyl)-3-fluorophenylene).

These cells exhibited specific charge capacities between 9.3-13.6 mAh/gand energy densities of 24.65-38.0 mWh/g, based on the total active massof the anode and cathode. The average cycling efficiency, calculatedfrom the charge retained after a maximum of 100 cycles, was 98.17%. Asshown in FIG. 9, the discharge curve exhibits an extended region atvoltages between 2.0 and 2.75 V, consistent with the value expected fromthe cyclic voltammograms of the two polymers.

The above-described performance of the electrochemical cells wascharacterized by recording multiple charge/discharge cycles of severalsample cells. The procedure for charging and discharging was as follows.The cells were charged at a constant current of 20 to 1000 μA/cm² up to3.25 V and held at this voltage until the current dropped to a valuebetween 10 and 100 μA/cm². At this point, the cells were discharged at aconstant current of 20 to 1000 μA/cm² until the cell voltage dropped to1.0 V. This procedure corresponds to theoretically 100% depth of chargeand discharge. FIG. 10A shows the relationship between discharge timeand voltage and FIG. 10B shows both the relations between charge timeand voltage (dotted line) and discharge time and voltage (solid line)for batteries prepared in accordance with this Example.

Although the present invention has been described in detail withreference to its presently preferred embodiments, it will be understoodby those of ordinary skill in the art that various modifications andimprovements to the present invention are believed to be apparent to oneskilled in the art. The embodiments were chosen and described in orderto explain the principles of the invention and its practical applicationto thereby enable others skilled in the art to best utilize theinvention in various embodiments and with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the invention be defined by the claims appended hereto.

What claimed is:
 1. An electrochemical storage cell comprising an anodeelectrode and cathode electrode, wherein one or both of the anode andcathode electrodes comprises at least one phenylenethienyl based polymerselected from the group consisting of poly(1,4 bis(2-thienyl)-benzene),poly(1,4-bis(2-thienyl)-2,5-fluorophenylene),poly(1,4-bis(2-thienyl)-3,6-difluorophenylene), andpoly(1,4-bis(2-thienyl)-2,3,5,6-tetrafluorophenylene).
 2. Anelectrochemical storage cell according to claim 1, wherein the cathodeelectrode comprises at least one phenylene-thienyl based polymerselected from the group consisting of poly(1,4 bis(2-thienyl)-benzene),poly(1,4-bis(2-thienyl)-3-fluorophenylene), poly(1,4-bis 2-thienyl)-2,5-difluorophenylene), and poly(1,4-bis(2-thienyl)-2,3,5,6-tetrafluorophenylene).
 3. An electrochemical storagecell according to claim 2, wherein the cathode electrode comprisespoly(1,4-bis (2-thienyl)-3- fluorophenylene) as the phenylene-thienylbased polymer.
 4. An electrochemical storage cell according to claim 1,wherein one or both of the anode and cathode electrodes furthercomprises at least one fluorophenyl polythiophene selected from thegroup consisting of poly(3(2-fluorophenyl)thiophene),poly(3(3-fluorophenyl)thiophene), poly(3(2,4-difluorophenyl)thiophene),poly(3(3,4-difluorophenyl)thiophene),poly(3(3,5-difluorophenyl)thiophene), andpoly(3(3,4,5-trifluorophenyl)thiophene).
 5. An electrochemical storagecell according to claim 4, wherein the anode electrode comprises atleast one fluorophenyl polythiophene selected from the group consistingof poly(3(2-fluorophenyl)thiophene), poly(3(3-fluorophenyl)thiophene),poly(3(2,4-difluorophenyl)thiophene),poly(3(3,4-difluorophenyl)thiophene),poly(3(3,5-difluorophenyl)thiophene), andpoly(3(3,4,5-trifluorophenyl)thiophene).
 6. An electrochemical storagecell according to claim 5, wherein the cathode electrode comprises atleast one phenylene-thienyl based polymer selected from the groupconsisting of poly(1,4-bis(2-thienyl)-3-fluorophenylene),poly(1,4-bis(2-thienyl)-2,5-difluorophenylene),poly(1,4-bis(2-thienyl)-2,3,5,6-tetrafluorophenylene) and poly(1,4bis(2-thienyl)-benzene), andwherein the cathode electrode comprises atleast one fluorophenyl polythiophene selected from the group consistingof poly(3(2-fluorophenyl)thiophene), poly(3(3-fluorophenyl)thiophene),poly(3(2,4-difluorophenyl)thiophene),poly(3(3,4-difluoro-phenyl)thiophene),poly(3(3,5-difluorophenyl)thiophene), andpoly(3(3,4,5-trifluorophenyl)thiophene).
 7. An electrochemical storagecell according to claim 6, wherein the anode electrode further comprisesat least one phenylene-thienyl based polymer selected from the groupconsisting of poly(1,4-bis(2-thienyl)-3-fluorophenylene),poly(1,4-bis(2-thienyl)-2,5-difluorophenylene),poly(1,4-bis(2-thienyl)-2,3,5,6-tetrafluorophenylene), and poly(1,4bis(2-thienyl)-benzene).
 8. An electrochemical storage cell according toclaim 5, wherein the anode electrode comprisespoly(3(3,4,5-trifluorophenyl)thiophene as the fluorophenylpolythiophene.
 9. An electrochemical storage cell according to claim 1,wherein the at least one phenylene-thienyl based polymer is formulatedby electropolymerization.
 10. An electrochemical storage cell accordingto claim 1, wherein the at least one phenylene-thienyl based polymer isformulated by chemical polymerization.
 11. An electrochemical storagecell according to claim 1, further comprising a polymer gel electrolyteinterposed between the anode and cathode electrodes, wherein the polymergel electrolyte comprises a polymer component, a salt and an organicsolvent or solvent mixture.
 12. An electrochemical storage cellaccording to claim 11, wherein the polymer component is poly(acrylonitrile), the salt is tetrabutylammonium tetrafluoroborate, andthe organic solvent is propylene carbonate.
 13. An electrochemicalstorage cell according to claim 11, wherein the organic solvent ispropylene carbonate.
 14. An electrochemical storage cell according toclaim 11, wherein the organic solvent is sulfolane.
 15. A batterycomprising at least one of the electrochemical storage cells of claim 1.16. An electrochemical storage cell comprising an anode electrode andcathode electrode,wherein the cathode electrode comprises at least onephenylene-thienyl based polymer selected from the group consisting ofpoly(1,4-bis(2-thienyl)-3-fluorophenylene),poly(1,4-bis(2-thienyl)-2,5-difluorophenylene),poly(1,4-bis(2-thienyl)-2,3,5,6-tetrafluorophenylene) and poly(1,4bis(2-thienyl)-benzene), and wherein the anode electrode comprises atleast one fluorophenyl polythiophene selected from the group consistingof poly(3(2-fluorophenyl)thiophene), poly(3(3-fluorophenyl)thiophene),poly(3(2,4-difluorophenyl)thiophene),poly(3(3,4-difluorophenyl)thiophene),poly(3(3,5-difluorophenyl)thiophene), andpoly(3(3,4,5-trifluorophenyl)thiophene).
 17. An electrochemical storagecell according to claim 14, wherein the cathode electrode comprisespoly(1,4-bis(2-thienyl)-3-fluorophenylene) as the phenylene-thienylbased polymer, and wherein the anode electrode comprisespoly(3(3,4,5-trifluorophenyl) thiophene as the fluorophenylpolythiophene.
 18. An electrochemical storage cell according to claim16, wherein the at least one phenylene-thienyl based polymer and the atleast one fluorophenyl polythiophene are formulated byelectropolymerization.
 19. An electrochemical storage cell according toclaim 16, wherein the at least one phenylene-thienyl based polymer andthe at least one fluorophenyl polythiophene are formulated by chemicalpolymerization.
 20. An electrochemical storage cell according to claim16, further comprising a polymer gel electrolyte interposed between theanode and cathode electrodes, wherein the polymer gel electrolytecomprises a polymer component, a salt and an organic solvent or solventmixture.
 21. An electrochemical storage cell according to claim 20,wherein the polymer component is poly (acrylonitrile), the salt istetrabutylammonium tetrafluoroborate, and the organic solvent ispropylene carbonate.
 22. An electrochemical storage cell according toclaim 20, wherein the organic solvent is propylene carbonate.
 23. Anelectrochemical storage cell according to claim 17, wherein the organicsolvent is sulfolane.
 24. A battery comprising at least one of theelectrochemical storage cells of claim
 16. 25. An electrochemicalstorage cell comprising:an anode electrode and cathode electrode, one orboth of the anode and cathode electrodes comprises at least onefluorophenyl polythiophene selected from the group consisting ofpoly(3(2-fluorophenyl)thiophene), poly(3(3-fluorophenyl)thiophene),poly(3(2,4-difluorophenyl)thiophene),poly(3(3,4-difluorophenyl)thiophene),poly(3(3,5-difluorophenyl)thiophene), andpoly(3(3,4,5-trifluorophenyl)thiophene); and a polymer gel electrolyteinterposed between the anode and cathode electrodes, the polymer gelelectrolyte comprising a polymer component, a salt, and an organicsolvent selected from the group consisting of propylene carbonate andsulfonate.
 26. An electrochemical storage cell according to claim 25,wherein the organic solvent is propylene carbonate.
 27. Anelectrochemical storage cell according to claim 25, wherein the organicsolvent is sulfolane.
 28. An electrode comprising at least onephenylenethienyl based polymer selected from the group consisting ofpoly(1,4-bis(2-thienyl)-3-fluorophenylene),poly(1,4-bis(2-thienyl)-2,5-difluorophenylene),poly(1,4-bis(2-thienyl)-2,3,5,6-tetrafluorophenylene), and poly(1,4bis(2-thienyl)-benzene).
 29. A method for producing an electrochemicalstorage cell, comprising the steps of:a) forming a cathode electrodestructure from an electronically conducting polymer, wherein theelectronically conducting polymer comprises at least onephenylene-thienyl based polymer selected from the group consisting ofpoly(1,4-bis(2-thienyl)-3-fluorophenylene),poly(1,4-bis(2-thienyl)-2,5-difluorophenylene),poly(1,4-bis(2-thienyl)-2,3,5,6-tetrafluorophenylene), and poly(1,4bis(2-thienyl)-benzene); b) forming an anode electrode structure; c)formulating a polymer gel electrolyte comprising a polymer component, asalt, and an organic solvent or solvent mixture; d) incorporating thepolymer gel electrolyte between opposing surfaces of the cathode andanode electrode structures; and e) combining the cathode electrodestructure, anode electrode structure, and polymer gel electrolyte toproduce the electrochemical storage cell.
 30. An electrochemical storagecell produced according to the method of claim
 29. 31. A methodaccording to claim 29, wherein the organic solvent is propylenecarbonate.
 32. A method according to claim 29, wherein the organicsolvent is sulfolane.